1. Field of the Invention
The present invention relates to an image recording method, an ink set, and a recorded material.
2. Description of the Related Art
In the field of recording media and inks for use in inkjet recording, various techniques have been proposed in order to form a high-quality image having improved color density, fixing properties and fineness.
However, since there are various kinds of recording media, including plain paper, there may be problems in that the quality of the recorded image in terms of fixing properties, fineness or the like may not be sufficiently achieved or curling of the recording medium may occur after the recording. For example, when recording is performed using an aqueous ink on a recording medium for use in an ordinary printing process, including “coated paper” such as art paper or coated paper or “non-coated paper” such as book paper, it is known that deformation of paper called curling may caused by severance or reconnection of hydrogen bonds in cellulose fiber contained in the paper, due to the moisture contained in the aqueous ink.
On the other hand, as the inkjet recording speed increases, recording media are required to adapt to a single-path recording system, in which recording can be performed at high speed by a single operation of a recording head, rather than a shuttle-scan system. In the single-path system, the ink needs to be rapidly absorbed in the recording medium. However, when a large amount of ink is applied to the recording medium upon formation of a solid image or the like, curling tends to be caused since a large amount of solvent contained in the ink is absorbed in the recording medium.
Although some techniques have been proposed in order to suppress the curling of the recording medium, for example, by adding an anti-curling agent such as sugar to the ink, or by increasing the forth of a system in a delivery section at which the recording medium is restricted from moving, sufficient effects of suppressing curling have yet be achieved.
Japanese Patent Application Laid-Open (JP-A) No. 2004-136458 discloses a method of suppressing curling by applying a liquid containing alcohol to a recording medium prior to conducting recording with ink, and then recording an image to the recording medium using ink in such a manner that the recording medium is substantially dried at a recording position. However, according to this method, cissing of ink or bleeding in the image may be caused by the alcohol that has been applied to the recording medium before the application of the aqueous ink. If the surface of the recording medium after the alcohol-containing liquid has been applied is dried in order to overcome the above problem, curling caused upon application of ink in the subsequent step may not be prevented.
JP-A No. 9-254376 discloses an inkjet printing method in which a pretreatment liquid is applied to a recording medium in a separate step from that of ink, in order to suppress the penetration of ink in the recording medium. However, according to this method, while suppressing the penetration of a colorant (pigment) in the ink by insolubilizing the colorant by the action of a component such as a cationic active agent in the pretreatment composition, penetration of a solvent (water) in the ink that does not react with the pretreatment composition may not be suppressed. Consequently, curling of the recording medium cannot be suppressed.
U.S. Pat. No. 6,283,589 discloses a method in which a recording medium is made liquid-repellent prior to application of ink. However, according to this method, while suppressing the penetration of ink, the capillary action for a solvent in the ink may be reduced to suppress spreading of ink dots. Therefore, spaces may be formed between the ink dots to significantly reduce the optical density of the image and unevenness due to mislocation of ink dots may be exaggerated, thereby failing to obtain a high-quality image.
In view of the above-mentioned circumstances, the present invention provides an image recording method that can form an image with high reproducibility while suppressing curling, an ink set for use in the image recording method, and a recording material obtained in the image recording method.
It is known that in an image recording process using an aqueous pretreatment composition containing a relatively large amount of water and an aqueous ink in combination, curling, which occurs upon application of the aqueous ink, tends to be caused by the penetration of water or an aqueous solvent into a recording medium to sever hydrogen bonds in cellulose that composes the recording medium. The present invention has been made in view of the findings that by forming a film on the recording medium that can block the penetration of water the like into the recording medium prior to applying the aqueous ink in such a manner that the absorption of solvent that tends to sever the hydrogen bonds in cellulose is suppressed to a low level, curling can be suppressed and a high-quality image can be formed at the same time.